Role of Rhophilin2, a RhoB GTPase effector, in melanoma metastasis: zebrafish as a model

Supervisor: Dr. Isabelle Pirson

RhoGTPases regulate the cellular processes that need cytoskeleton dynamics or vesicular trafficking regulation and play key roles in cancer development. Among their effectors, Rhophilin-2 (Rhpn2) is a specific partner of activated RhoB proteins and is modulated in various cancer. Interestingly, RhoB KO mice are more susceptible to induced skin cancer. Less is known about Rhophilin2 biological mechanisms of action or physiological roles. 

In the present project, we propose :

–        In human melanoma cancer cells lines, to investigate the role of Rhpn2 in cellular migration/invasion processes and in exosome synthesis through stable knock-down (shRNA) or overexpression (lentiviral) of Rhpn2. The metastatic properties of these cells will then be assessed through in vivo xenografts experiments in zebrafish. 

–        In zebrafish, to generate KI models expressing fluorochrome reporters under the control of Rhpn2 promoters to detail tissue and subcellular expression profiles of Rhpn2 in embryos and adults. We will also induce melanoma in already available Rhpn2KO fishes compared to wt to evaluate the role of Rhpn2 in tumor growth and metastasis. 

–        By biochemical experiments, to unravel the proteic partners of Rhpn2 to decipher the molecular function of this protein. Our previous two-hybrid work also allowed the characterization of potential interactors. A tetraspanin, involved in exosome generation, was also identified as a Rhpn2 partner. This will be studied as a potential event for cancer progression. 

Rho proteins are important regulators of the cytoskeleton and are of major importance in membranar trafficking in cancer cells underlining the importance of studying Rhophilin involvement in cancer development.

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